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Workshop of European Group on Ultrarelativistic Heavy Ion Physics

from STAR to ALICE

Close velocity Correlations

Jan Pluta, Warsaw University of Technology

JINR, Dubna9-14. 03. 2006

The starting pointThe starting point

Podgorecki, Kopylov, SmorodinskiDubna, 1974

Weekly meeting of propane bubble chamber group.

1981Lednicky and Lyuboshitzsolved the problem of final state interaction

1972 - 4Kopylov and Podgoretskysettled the basics of correlation femtoscopy:•correlation function,•mixing technique,•role of space-time charakterist...

1975 ...Grishin, propane bubble chamber group and others in Dubna - measured the two-particle correlations

qout

qside

qlong

Rsi

de

R long

Rout

x1

x2

12 ppq

p1

p2

q

12 pp2

1k

Two-particle interferometry: p-space separation space-time separation

• HBT: Quantum interference between identical particles

pairsevent mixed

pairsevent real

)(P)(P

),(P),(

21

2121

pp

ppppC

2long

2long

2side

2side

2out

2out)(1),(

RqRqRqekkqC

q (GeV/c)q (GeV/c)

C (

q)

C (

q)

11

22R

1~

– Final-state effects (Coulomb, strong) also can cause correlations, need to be accounted for

Gaussian model (3-d):

The basic notions

HBT at RHIC...HBT at RHIC...

HBT Excitation Function

“RHIC HBT puzzle”

•unexpected (small) sizes

•Rout/Rside = (approx.)1

•Pt dependence do not agree with models

•The same Pt dependence for pp, dAu and AuAu

STAR 130 GeV

PHENIX 130 GeV

RHIC/AGS/SPS Systematics<kT>≈ 400 MeV (RHIC) <kT>≈ 390 MeV (SPS)

Lisa

, P

ratt

, S

oltz

, W

iede

man

n, n

ucl-e

x/05

0501

4

STAR DATASTAR DATA (pp,dAu,CuCu,AuAu@62GeV - prelim.)

Pion HBT radii from different systems and at different energies

scale with (dNch/dη)1/3

Z.Chajęcki, QM’2005

System expansion: System expansion: Initial vs Final Initial vs Final SizeSize

Proton initial size = 0.89 fm from e-scattering

Smooth expansion of the system from p+p to Au+Au

AuAu: system expands

pp (dAu): no or less expansion

Collisions at 200GeV only

Transverse mass dependenceTransverse mass dependence in in AuAu++AuAu

In Au+Au pT (mT) dependence attributed to collective expansion of

the source

0.3 0.30.4 0.40.5 0.50.2 0.2 0.6

STAR, Au+Au@200GeV, PRC 71 (2005) 044906

.2

Calc. with Blast-Wave -Retiere, Lisa, PRC 70 (2004)

044907

0.

0.

0.

Consistency check on flow – Consistency check on flow – kaonskaons

Hania Gos, Kromeriz’05

More confirmationMore confirmation

STAR preliminary

Surprising („puzzling”) scalingSurprising („puzzling”) scaling

All pT(mT) dependences of

HBT radii observed by STAR

scale with pp although it’s

expected that different

origins drive these

dependences

HBT radii scale with pp

Scary coincidence or something deeper?

pp, dAu, CuCu - STAR preliminary

Ratio of (AuAu, CuCu, dAu) HBT radii by pp

Hania Gos, Kromeriz’05

Nonidentical particle correlations – the asymmetry analysis

k*

1

Catching up•Effective interaction time larger•Stronger correlation

Moving away•Effective Interaction time smaller•Weaker correlation

“Double” ratio•Sensitive to the space-time asymmetry in the emission process

R.Lednicky, V. L.Lyuboshitz,B.Erazmus, D.Nouais,Phys.Lett. B373 (1996) 30.

C-

C+

C+C-

Kinematics selectionalong some directione.g. kOut, kSide, cos(v,k)

Heavier particlefaster

Lighter particlefaster

Adam Kisiel,Fabrice Retiere

Pion-Kaon at 200 AGeV

• Good agreement for same-charge combinations

• Clear emission asymmetry signal

Out double ratio

Side double ratio

Sigma: 17.3 ± 0.8 fm

Mean: -7.0 ± 1.2 fm

STARpreliminary

+ 0.9 syst.- 1.6 syst.

+ 6.1 syst.- 4.0 syst.

kaon faster pion faster

STARpreliminary

Λ peaks

Mean: -7.4 ± 0.9 fm

Sigma: 15.1 ± 0.4 fm

Pion-Proton 130 AGeV• Good agreement

for identical and opposite charge combinations

• We observe Lambda peaks at k*~decay momentum of Λ

Out double ratio

Side double ratio

+ 1.0 syst.- 1.5 syst.

- 3.4 syst.+ 1.9 syst.

Fit assumes source is a gaussian in r*out

proton faster pion faster

Hania Gos, Kromeriz’05

Origins of asymmetry

• Measures asymmetry in pair rest frame is a combination of time and space shifts in source frame

• In heavy-ion collisions one expects difference in emission time from resonance decays

pion average = 16.1kaon average = 14.8time shift = 1.3

pion pion emissionemissiontimestimes

kaon kaon emissionemissiontimestimes

primordialprimordial

allall

allall

primordialprimordial

THERMINATORcalculation

Adam Kisiel, Kromeriz’05

Space asymmetry from flow

• Transverse momentum of particles is composed of the thermal (randomly distributed) and flow (directed “outwards”) components

• With no flow average emission point is at center of the source and the length of homogeneity is the whole source

• Flow makes the source smaller (“size”-p correlation) AND shifted in outwards direction (x-p correlation)

• For particles with large mass thermal motion matters less – they are shifted more in “out” direction. The difference is measured as emission asymmetry.

pion pion emissionemissionpointspoints

kaon kaon emissionemissionpointspoints

protonproton emissionemissionpointspoints

outoutsideside

THERMINATOR calculation

Fourier coefficients of HBT() oscillations

Rx

Ry

initi

al =

final

STAR Collaboration, nucl-ex/0312009

• Out-of-plane sources at freeze-out– Pressure and/or expansion

time was not sufficient to quench initial shape

• From v2 we know...– Strong in-plane flow →

significant pressure build-up in system

Short expansion time plays dominant role in out-of-plane freeze-out source shapes

eccentricity

Time

2x

2y

2x

2y

RR

RR

Dmitri Peresounko Direct photon interferometry

PHENIX; d+Au collisions at √sNN=200 GeV

ImagingTechniqueImagingTechnique

Technique Devised by:

D. Brown, P. Danielewicz,PLB 398:252 (1997). PRC 57:2474 (1998).

Inversion of Linear integral equation to obtain source function

20( ) 1 ) (,4 ( )C K q r S rq drr

Source Source functionfunction

(Distribution of pair separations)

Encodes FSI

CorrelationCorrelationfunctionfunction

Inversion of this integral equation== Source Function

Emitting source

1D Koonin Pratt Eqn.

Paul Chung, Stony Brook

Nature hides her secrets in data (D)

Question 0: Do the models (E,F,G,H) describe the data?Answer 0: These models fail, but this is not a puzzle.

Q. 1: Are any other models that descibe the data?A. 1: Yes, there are three models (A,B,C) that

cannot be excluded (Conf. Lev. > 0.1 %)

Q. 2: Do these models have anything in common?A. 2: Yes, and this where the data (D) are.

This common part is what Nature is trying to tell us.

D Model B

Model A

Model H

Model G

Model E

Model F

Model C

T.Csorgo, Kromeriz’05

Rewiew of Bose-Einstein/HBT Correlationsin high energy heavy ion physics

Acceptable

Comparison of results of models

Comparison of results of models

Comparison of results of models

Comparison of results of models

Comparison of results of models

Comparison of results of models

Comparison of results of models

Comparison of results of models

Comparison of results of models

Comparison of results of models

Acceptable

Comparison of results of models

Comparison of results of models

~Acceptable

Comparison of results of models

~Acceptable

Comparison of results of models

The HBT test Less unpromising models: don’t fail fitting Au+Au HBT data @ RHIC

– nucl-th/0204054 Multiphase Transport model (AMPT)Z. Lin, C. M. Ko, S. Pal

– nucl-th/0205053 Hadron rescattering model`` T. Humanic

– nucl-th/0207016 Buda-Lund hydro (hep-ph/9503494, 9509040) T. Csorgo, B. Lörstad, A. Ster et al.

(nucl-th/0403074, /0402037, /0311102 )

– hep-ph/0209054 Cracow model (single freeze-out, thermal)W. Broniowski, A. Baran, W. Florkowski

– nucl-ex/0307026 Blast wave model (Schnedermann, Heinz)M. A. Lisa, F. Retiere, PRC70, 044907 (2004)

– hep-ph/0404140 Time dependent Duke hydro model T. Renk

– nucl-th/0411031 Seattle model (quantum opacity)J. G. Cramer, G. A. Miller, J.M.S. Wu, J.-H. Yoon

– nucl-th/0507057 Kiev-Nantes modelBorysova, Sinyukov, Akkelin, Erazmus, Karpenko

-> More restrictive tests are needed: spectra, v2, HBT, dn/dy

T.Csorgo, Kromeriz’05

Successfull models at RHIC (1): Blastwave

F. Retiere, nucl-ex/0405024; F. Retiere and M. A. Lisa, nucl-th/0312024

Spectra

v2

HBT

T=106 ± 1 MeV

<InPlane> = 0.571 ± 0.004 c

<OutOfPlane> = 0.540 ± 0.004 c

RInPlane = 11.1 ± 0.2 fm

ROutOfPlane = 12.1 ± 0.2 fm

Life time () = 8.4 ± 0.2 fm/c

Emission duration = 1.9 ± 0.2 fm/c

2/dof = 120 / 86

(Errors are statistical only, CL = 0.91 %)

Neglect of resonances

Successfull model (2): Cracow model

nucl-th/0212053

Model features:

Thermal model included(abundances driven by Tchem and B)

Assumes full Hubble flow

Sudden freeze-out(at a constant proper-time)

Single freeze-out, Tchem = Tkin

Boost-invariance

All resonances included, they decay but do not rescatter.

Future plans at LHC

RHIC/AGS/SPS Systematics<kT>≈ 400 MeV (RHIC) <kT>≈ 390 MeV (SPS)

...and expectations for LHC

Assuming the same tendency:

40961/3=1680001/3=20

Rexpected < 10fm

Pion freezeout times are about twice as long at LHC compared to RHIC

Tom Humanic, Kromeriz’05

Pion freezeout time and z-position for LHCform rescattering calculations

Projected 3D two-pion C2 for LHC Pb+Pb from rescattering

for b=8 fm centrality and pT bin 0-200 MeV/c

Two-pion correlation function for LHCform rescattering calculations

Transverse radius parameters for LHC vs. RHIC

Transverse radius parameters are somewhat larger and show a strongerpT dependence for LHC compared with RHIC

RLong and parameters for LHC vs. RHIC

RLong for LHC is almost twice as large as for RHIC reflectinglonger freezeout times;

behaves about the same at LHC and RHIC

Current status of momentum correlation analysis

1. „HBT-analyser” – a dedicated sofrware for momentum coorelation

analysis at ALICE - ready and integrated in Ali-root environment

2. Experimental factors specific for correlation analysis: track

splitting, merging, two-particle resolution and PD - evaluated for

different two-particle systems

3. Universal fitting procedure for identical and nonidentical particles

„Corfit” – ready, but not integrated yet in Ali-root environment

4. Influence of hard processes (jets) on particle correlatins – under

investigations

5. Single event pion interferometry will be possible at ALICE

Results of PPR preparation; Chapter 6.3 Momentum Correlations

Current status of momentum correlation analysis

For details see:ALICE-INT-2005-026, One and two-particle resolution and PID

ALICE-INT-2005-031, Two-tracks effects at ALICE

ALICE-INT-2005-045, Some specific features of momentum correlations to be seen at ALICE (draft-0)• Formalism of two-particle correlations• Particle correlations for expanding sources• Role of Coulomb and strong final state interactions• Nonidentical particle correlations and space-time asymmetries• Azimuthally sensitive HBT• Formation of light (anti)nuclei• Multi-particle Coulomb effects • Correlation measurements of two-particle scattering• Influence of resonance decays on two-particle correlations

Some examples

Simulation chain for particle correlations

Two Particle Resolutions

Resolution (r.m.s) [MeV]

Qinv Qout Qside Qlong

PDC04 TPPDC0

4 TP PDC04 TP PDC04 TP

+ 0.9 1.3 3.4 3.8 0.4 0.4 1 0.8

2.3 4.2 6.4 9.5 0.6 0.5 1.9 2.3

pp 4.0 8.0 9.4 13.0 0.8 0.7 3.2 4.3

-  x x 4.4 4.1 1.2 0.7 1.7 1.1

p  x x 5.8 4.2 2.1 0.7 1.8 1.2

p  x x 6.4 8.3 1.9 1.0 2.6 3.2

Almost the same results after ten years of work – very well ( ! ) :reasonable first estimation, and very good complete reconstruction.

Compare the results presented in „Technical Proposal” (TP, in 1995)and obtained from PDC04 (in 2005)

Piotr Skowroński

Track Merging

• Anti-Merging cut as implemented by STAR– Cutting on average distance between two tracks in TPC

– Space coordinates of tracks are calculated assuming helix shape using track parameters as reconstructed in the inner part of TPC

Single event pion-pion interferometry (with FSI)... by Zbyszek Chajęcki, (ro=8fm)

Single event pion-pion interferometry by Hania GOS

We are looking forward, working,

and waitingfor the first event of ALICE

Two-particle kinematics

LCMS: (P1+P2)z=0

Getting quantitative -Getting quantitative -What can be probed through fitting?What can be probed through fitting?

Source ofparticle 1

Source ofparticle 2

Boost to pair rest frame

When fitting “double-ratios” two independent variables are accessible:- Mean shift (<r*>) or μ- Sigma (r*)

r* =pairr–pairtr* separation in pair rest frameFunction of pair(pair)

Separation between source 1 and 2 in pair rest frame

r

r [fm] r* [fm]

Two important events;sources of informationand discussion forum:

Quark Matter Conferenceand

satellite topical meeting.